This is one of several recipes I learned in high school (yes, that long ago). I cannot remember which cookbook I got it from, I wish I could, some of the recipes in it dated back to the 1920s/1930s, most were excellent and fairly easy to prepare with common ingredients. As I have been a lifelong fan of puddings, I made sure I never lost this recipe.
1 cup … sugar
6 tbsp … flour
3/4 tsp … salt
4 cups … milk (I have always said “fat be ded" and used whole milk for this one)
4 tbsp … butter or margarine (butter is highly superior IMO, again "fat be ded”)
1 tsp … vanilla
Blend sugar, flour and salt in top of double boiler.
Heat milk in microwave, 1 minute per cup (saves time over the original heating technique, and makes it less likely that the milk will burn).
Stir warm milk into sugar mixture and cook over hot water until thick, about 10
minutes, stirring frequently (be careful not to burn the milk).
Beat eggs in small bowl.
Stir about 1/2 cup of hot mixture into eggs (must be done this way unless you want scrambled eggs in your milk mixture).
Pour eggs and mixture into double boiler, slowly and beating rapidly (slow and steady wins the race).
Stir and cook for 4 or 5 minutes, or until thick (check thickness by adherence to a metal spoon dipped into the mixture).
Remove from heat.
Add butter and vanilla and stir until smooth.
Chill in the refrigerator until it is set to your liking.
I have always used glass bowls (a personal quirk, as I am not a fan of plastic dishes) to chill the custard.